As Neil Tennant has helpfully pointed out, this album is called Introspective because all its songs are introspective. Truthfully, this isn't saying much – introspection is what Pet Shop Boys do. After all, their signature hit starts "When I look back upon my life …" and most of their great records involve a certain amount of self-reflection, which they frame with glorious disco-inspired pop. The resulting distance – the horribly familiar inability to stop questioning yourself, even in the middle of joy – used to be misread as irony. Then in 1990 the band made Behaviour, where Tennant sounded more honest and vulnerable than he ever had, and people called it their first great album. It is a great album – but for me the six long tracks of Introspective from 1988 are more rewarding.

You could hear the album as a journey away from distance. It starts with Left to My Own Devices, pop's greatest celebration of ambivalence. On the rest of side one we experience the downside of autonomy – a lonely Tennant conceding the need for companionship on I Want a Dog, then failing to connect to a lover on Domino Dancing. On side two he's redeemed – pledging himself on I'm Not Scared, admitting his faults on Always on My Mind, and finally opening out to the world on It's Alright. In the end, Introspective rejects its title.

That's why I still love it, but not why I fell for the album in the first place. I was 15, awkward, mistrustful of dance music, adrift from pop. Introspective changed that – it's a collection of extended mixes for songs that mostly weren't yet singles, and these longer versions are the definitive ones. I know now that a lot of this album draws inspiration from years of fabulous, opulent disco mixes. But at 15 it was a beautiful education in what you could do with pop given space and ideas. Left to My Own Devices inverts itself, scrambles its earlier verses and takes off to a private, string-soaked dream world. I Want a Dog turns from a squib into something profoundly sad. The Sterling Void cover It's Alright is a nine-minute love letter to house music.

Best of all is the longer Always on My Mind, where the band gradually skeletonise the song, lose touch with it entirely and then, after seven minutes, drop in the riff and flood the track with colour. It was my introduction to the breakdown – dance music's greatest gift to the world – and it set my music taste back on track. That's still my favourite moment in all pop – and the emotional crux of a rich, hopeful record.

Or you could simply star rate it, or add it to one of your album lists. There are more than 3m new pages for you to explore as well as 600,000-plus artists' pages – so if, for example, the Human League are more your thing, or Erasure or even Electronic, then find their albums and get to work …

Continuing our new series in which Guardian and Observer writers pick their favourite albums ever – with a view that you might do the same – Kitty Empire hails some casual sexism and eye-rolling double entendres. Oh, and those riffs ...